Try a newer version though -- GDB 7.2 has been out for a (short) while
now. You're missing 2.5 years of development. If still unsuccessful with
a pristine release from ftp.gnu.org, then file a bug report at
http://sourceware.org/gdb/bugs/.

After more though, I think you may have to configure with
--enable-64-bit-bfd for a 32-bit gdb to work on 64-bit processes.
Although I have not actually tested that. In the past, I have just
built a native 64-bit gdb.